This research proposes to use a newly developed 3D ultrasound method to measure volume blood flow. A wide variety of clinical applications would benefit from this development including estimation of cardiac output, monitoring of cerebrovascular diseases, and evaluation of intrauterine growth restriction (IUGR) during pregnancy. Methods currently used are either invasive (i.e. insertion of a Swan-Ganz catheter) or have limited accuracy (i.e. unknown Doppler angle, vessel geometry, and flow profile). Therefore the goal of this project is to verify the performance of an angle-independent, robust, volumetric flow measurement technique that can be implemented within current clinical scanner architecture. The advent of 3D/4D ultrasound systems has made this prospect a reality and the research will serve to move non-invasive ultrasonic volume flow measurements to clinical application. The method proposed takes advantage of the Doppler firings commonly used in ultrasound systems. Because ultrasound imaging has expanded to 3D, a surface can be defined through a vessel in which the summation of the Doppler velocities will yield the volume flow. This method requires no a priori knowledge of the flow direction (angle independent) or vessel geometry and only that the surface completely intersect the vessel of interest. This is a substantial improvement over previous methods including those originally proposed in this project and uses Doppler information that has proven to be accurate in clinical blood velocity measurements. This is an extension of such measurements to 3D and the realization that such an extension provides the information needed for volume flow. This technique has already demonstrated volume flow measurements in steady state and pulsatile flow in phantoms and in arterial flow in a canine model. The proposed work will 1) verify these results over a range of flow conditions anticipated in vivo 2) make direct comparisons to a standard flow measurement technique in animals studies and 3) perform a pilot study quantifying flow in grafts of human subjects undergoing dialysis. The successful conclusion of these studies will be the verification of a system suitable for clinical use in the measurement of volume blood flow and understanding of the fundamental Doppler processing needed for more general implementation of the method. PUBLIC HEALTH RELEVANCE: The measurement of volume blood flow is critical in many clinical applications and would be readily employed in clinical practice if the measurement could be obtained easily and reliably. As just one example, loss of blood flow through the carotid leading to the brain has been identified as a potential cause in 20-30% of all strokes. Current methods commonly used to measure changes in blood flow require the insertion of measurement devices into the circulation with the associated potential complications;however, the proposed 3D ultrasound imaging method proposed here would be noninvasive and may provide more accurate measurement of volume flow.